A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a vehicle is equipped with a navigation function to guide a driver to a destination through a calculated route. Such a navigation system detects the position of the user's vehicle, and reads out map data pertaining to an area at the current vehicle position from a data storage medium such as a DVD (digital versatile disc), a hard disc, etc. Typically, the navigation system displays a map image on a monitor screen while superimposing thereon a mark representing the current vehicle location. At an intersection, the navigation system notifies the user which direction to turn at the intersection.
Typically, such a navigation system is designed so that the user is able to scroll the map image to see a map image at a desired location and pin-point such a desired location. For example, a user in a certain state scrolls the map image to search a camping area in the next state, or a user scrolls the map image back and force to find a favorite restaurant in the city he/she is to visit. The map scrolling may be performed by operating any feasible means such as directional keys formed on the panel, remote controller, or touch-screen of the navigation system.
FIGS. 1A and 1B are schematic diagrams showing an example of scrolling process of the map image on the display of the navigation system. In FIGS. 1A and 1B, the screen 11 of the navigation system displays a map image with various roads and indicators. FIG. 1A mainly shows an area with a main road 22 while FIG. 1B mainly shows an area with a main road 23. Although not shown, the user typically scrolls the map image by operating direction keys or a joy-stick of the navigation system.
A vehicle position VP indicates a current vehicle position on the map image, and a map scale indicator 19 shows a map scale of the current map image on the screen. The screen of FIGS. 1A and 1B also shows a cursor 12 which is used to point a desired location on the map image to zoom-in or zoom-out or find information such as icons and address data, etc., associated with the location. The user scrolls the map image of FIG. 1A in an upper left direction as shown by an arrow in the left side of FIG. 1A so that the navigation system changes the location to show the map image of FIG. 1B.
FIGS. 2A and 2B are schematic diagrams showing the scrolling operation to illustrate the problems involved in the conventional navigation system. In the example of FIGS. 2A and 2B, the vehicle position indicator VP indicates the current vehicle position (original position) which is set as a default position on the map image with respect to the map scrolling. The reference numbers 1-5 indicate an order and a position of each movement of the map scrolling. Namely, as the user scrolls the map image, the user has made a first stop at the location represented by the reference number 1. Similarly, the reference number 2 indicates the location of the second stop that the user has made in scrolling the map image.
The reference number 3 indicates the third stop, the reference number 4 indicates the fourth stop, and the reference number 5 indicates the fifth stop. Each line connecting the two locations indicates a path that the user has taken to scroll the map image between the two locations. In the typical navigation system, when the user presses a cancel button or performs its equivalent operation, the map image will snap back to the vehicle position VP.
Thus, in FIGS. 2A and 2B, by pressing the cancel key, the map image is able to quickly return to the original location (vehicle position VP) as indicated by the broken line. When the user no longer wants to continue the map scrolling, this function of quickly returning to the original position may be useful. However, suppose the user was almost successful to find a desired location but accidentally touches the cancel key or its equivalent, the map image snaps back to the original position VP, thus, the user loses the searched location. This is especially harmful, as in the case of FIG. 2B, after the user has taken a long time to find the area which is very far from the vehicle position VP. The user may not remember the area and it may be difficult to come back to the searched area to resume the search.
Thus, there is a need of a new map scrolling method which allows the user to easily view the previously viewed locations again. Moreover, it is desired that the user is able to return, one-by-one, to the previously viewed location that is believed to be relevant to the search in a short period of time.